1. Field of the Invention
The present invention relates to an air cleaner using an ionic wind generated upon application of voltage between a discharge electrode and a counter electrode.
2. Description of the Related Art
Air cleaners can be installed in a room to remove dust, cigarette smoke, and the like from the room air. Such air cleaners fundamentally include air circulating means and dust collecting means. The air circulating means conventionally includes an electric motor, a fan driven by the motor, and air ducts. This makes air cleaners relatively large in size and in weight.
When the same air cleaners are installed in the passenger compartment of an automobile, their large size and weight necessitate their being located on the rear board of the compartment. In the case of rear board installation, however, the air cleaners cannot immediately catch cigarette smoke from the driver and other dust from the front seats. Before smoke, etc. reaches the rear board, it contaminates passengers in the rear seats, the upholstering of the seats and ceiling, etc. The smoke, etc., also diffuses over a greater volume of air, thus necessitating larger air treatment capacities on the part of the air cleaners.
There is known in the art an air circulating means which generates an "ionic wind". The term "ionic wind" refers to the phenomenon in which air in the vicinity of a discharge electrode is ionized by a corona discharge, which ions then move by electrostatic force toward the counter electrode. During motion of the ions, a number of neutral molecules are scattered to produce a molecular flow, i.e., a wind. The ionic wind may have a speed of several meters per second, adjustable according to the voltage applied. When the corona discharge occurs, dust in the air is also ionized. This ionized dust can be collected on downstream electrodes by an electrostatic dust collecting means.
Japanese Unexamined Patent Publication (Kokai) No. 52-99799 discloses an ionic wind generating device including a discharge electrode, a grounded counter object, and an intermediate control electrode. The control electrode has a central opening through which ionic wind passes toward the object. According to this publication, uniform distribution of the ionic wind can be obtained from the opening to the object by making the slopes of the end configuration of the discharge electrode parallel to the opposing surfaces of the control electrode.
This type of ionic wind generating device cannot be used in an air cleaner, however, because the actual air cleaner must include a plurality of such devices in an air passage defined in a case of the air cleaner and the opposing surface of the control electrode defining the central opening obstructs the flow of air.
There is the further problem of the generation of ozone (O.sub.3) by the corona discharge. Ozone is toxic at high concentrations and, even at low concentrations, gives off an unpleasant smell. High voltages are required to generate sufficient ionic wind for a practical air cleaner, yet the higher the voltage, the larger amount of ozone generated.